AIMS: To assess the age-associated changes over time of plasma paraxanthine/caffeine (PAX/CAF) ratios used as a probe for CYP1A2 activity. METHODS: Intraindividual and interindividual variabilities in PAX/CAF ratio were compared by phenotyping with caffeine, 16 young and 16 elderly healthy subjects on five occasions. RESULTS: PAX/CAF ratio variability was comparable regardless of age (intraindividual CV: 17.6 +/- 6% and 16.2 +/- 5.9%, interindividual CV: 48.1 +/- 2.9% and 42.7 +/- 3.6% in young and elderly, respectively). The PAX/CAF ratio was lower in elderly than in young subjects (95% CI for the difference: 0.004, 0.32) but the difference was not significant in nonsmokers compared separately. CONCLUSIONS: The variability over time of the PAX/CAF ratio is not influenced by age.
AIMS: To assess the age-associated changes over time of plasma paraxanthine/caffeine (PAX/CAF) ratios used as a probe for CYP1A2 activity. METHODS: Intraindividual and interindividual variabilities in PAX/CAF ratio were compared by phenotyping with caffeine, 16 young and 16 elderly healthy subjects on five occasions. RESULTS:PAX/CAF ratio variability was comparable regardless of age (intraindividual CV: 17.6 +/- 6% and 16.2 +/- 5.9%, interindividual CV: 48.1 +/- 2.9% and 42.7 +/- 3.6% in young and elderly, respectively). The PAX/CAF ratio was lower in elderly than in young subjects (95% CI for the difference: 0.004, 0.32) but the difference was not significant in nonsmokers compared separately. CONCLUSIONS: The variability over time of the PAX/CAF ratio is not influenced by age.
Authors: M A Butler; N P Lang; J F Young; N E Caporaso; P Vineis; R B Hayes; C H Teitel; J P Massengill; M F Lawsen; F F Kadlubar Journal: Pharmacogenetics Date: 1992-06
Authors: Xia Yang; Bin Zhang; Cliona Molony; Eugene Chudin; Ke Hao; Jun Zhu; Andrea Gaedigk; Christine Suver; Hua Zhong; J Steven Leeder; F Peter Guengerich; Stephen C Strom; Erin Schuetz; Thomas H Rushmore; Roger G Ulrich; J Greg Slatter; Eric E Schadt; Andrew Kasarskis; Pek Yee Lum Journal: Genome Res Date: 2010-06-10 Impact factor: 9.043